Posted
by
BeauHDon Wednesday December 06, 2017 @05:00AM
from the icy-hot dept.

According to new research published today in Journal of Geophysical Research: Planets, Europa has what it takes to support plate tectonics. "Using computer models, a team lead by Brown University planetary scientist Brandon Johnson was able to demonstrate the physical feasibility of icy plates driving deep into the icy interior in a processes similar to what's seen on Earth," reports Gizmodo. "Excitingly, this same process could be delivering important minerals to the ocean below, heightening the moon's status a potentially habitable world." From the report: Europa has surface features reminiscent of Earth's mid-ocean ridges. For astronomers, this hinted at geological processes akin to subduction zones, where, on Earth, tectonic plates slide underneath another, sinking deep into the planet's interior. Several years ago, researchers Simon Kattenhorn and Louise Prockter posited this explanation when they noticed that a 20,000 square-kilometer (7,722 square-mile) chunk of ice had mysteriously disappeared from Europa's surface. Their explanation was that Europa's surface, like a gigantic jigsaw puzzle, is composed of tectonic plates, and that occasionally a plate of ice will sink beneath the other into warmer layers below. But this observational evidence of extension and spreading needed to be supported by geophysical reality. To that end, Johnson's team ran a computer simulation to see if it was possible for ice to sink in this way.

On our planet, subduction is primarily driven by differences in temperature between a descending slab and the surrounding mantle. Dense crustal material features a negative buoyancy that drives it down into the mantle. The Brown University scientists figured a similar thing happens on Europa, but with ice. In the case of Europa, the researchers surmised that the moon has two frozen layers -- an outer lid of very cold ice that sits above a layer of slightly warmer convecting ice. Their models showed that subduction is indeed possible in this alien environment, but only if the outer shell contains varying amounts of salt. This added ingredient provides the necessary density differences for a slab to conduct.

Most people who feel the need to add, 'for life as we know it' when the subject comes up seem to be ignorant of the reasons we have for believing it is probably very safe to say 'life' instead of 'life as we know it'.

No, Si can't replace C as a backbone for complex molecules. Yes, you need a liquid in which chemistry can happen. And a (fairly gentle) energy gradient - enough to help chemistry along without breaking molecules apart before anything interesting happens with them.

I think that one is possible. I can see that being humanity's legacy - creating such a 'species'.

I also think the fact that we've never found any evidence of such is probably a pretty good indication that the difficulty of traversing the void between stars is likely insurmountable even if you're an AI in radiation-hardened hardware.

I also think the fact that we've never found any evidence of such is probably a pretty good indication that the difficulty of traversing the void between stars is likely insurmountable even if you're an AI in radiation-hardened hardware.

I'm not sure that's right -- on a cosmic scale we really haven't been looking for all too long yet, and we're such a small target to hit - or put differently, the universe is so huge - that even with a viable means of bridging those distances, it wouldn't seem all too likely to be run into just by chance (especially not in the short timespan in which we could actually tell what's going on). For all I know, the various stories about gods and angels and whatever might as well be based on such encounters;)

The Earth - the one example of intelligent life in the Milky Way known to humanity - is ~4.5 billion years old, and it's taken ~4 billion years of that time to have us evolve on it to the point we can post about it on Slashdot. We don't know, however, if that's an unusually long time, or an unusually short time.

Hopefully it's long or average, because our star is near the end of it's current Earth-supporting phase. If you assume you need a Sun-like star (smaller gets you a longer-lasting star, but the habitable zone gets closer to requiring planets to be tidally locked, and stellar temperament becomes a problem, too), then you pretty much want to know people can pop up on an orbiting rock in less than 4 billion years.

Anyway, at speeds we can reach with our technology, it would take around 5 million years to cross the galaxy. 5 million years is peanuts compared to the 4 billion years life has been on Earth so far. Now consider there are probably ~10 billion potentially habitable worlds in the Milky Way based on our current models.

Only ONE of those 10 billion worlds has to have intelligent life begin to colonize the galaxy a mere 5 million years before we started talking about it to arrive by tea time tomorrow.

And the Sun wasn't the first star of its class to be born. There's at least one similar star we know of that's over 11 billion years old, which potentially means there's an extra 7 billion years of leeway for aliens to set up shop everywhere. Well, not everywhere - obviously if they were zipping around the Milky Way more than 4 billion years ago, Earth would just have been a hot damp rock. On the other hand, you'd expect that with the extra lead time, they'd be around pretty much every star in the sky and we'd have seen SOMETHING by now.

The real (and immense) difficulty is in getting enough photons into our detectors, because the distances are vast and unless you have some silly dream of planet-sized megastructures... anything we'd look for would be tiny.

> I think there's a lot more to crossing the galaxy in 5M years than velocity alone.

Agreed. But humans have gone from banging rocks together to the space and information age in 200,000 years. That's basically 'from scratch'. Now imagine you've arrived at a new planetary system having foreknowledge of the available resources, and brought all your tech know-how and a 'starter kit' with you.

I think you'd have to agree that the amount of time required to jump off to the next candidate planetary system wou

I bet you would like "The Vital Question" by Nick Lane. It's a very recent book that brings together quite a lot of phylogenetic, chemical, and geophysical evidence to show how like likely arose on Earth - the first plausible explanation of abiogenesis I've ever seen. Also, by his reasoning, the origin of life might not have been a fluke, but the first eukaryote - that's possibly a great filter.

Thanks for the super-important clarification. Just in case anyone was wondering - Europa is not being posited as a suitable planet for five-dimensional beings of pure energy, silicon based robo-life, or swarms of nano-machines.

Where from? The amounts of rock minerals from space dust and organics from reactions on the surface are probably minute. I suspect any significant minerals come from the moons core which AFAIK is thought to be made of rock.

Anyway, we have no idea what conditions are required for life to start. There may well be a minimum energy requirement which europa doesn't even get close to. Also you need some kind of energy gradiant. In an ocean sealed off dozens or even hundreds of km below the surface I suspect that gradient is shallow in the extreme.

Well if you consider numerous articles I've read on the subject and a science background nothing, then sure. But feel free to elaborate your ideas, if you have any and you're not just another A/C troll.

Well, then, since you feel qualified to weigh in on the amount of rocky mass recycled from the icy crust, off the top of your head you should be able to tell us the mass flux from impactors and space dust at Europa. What is it?

Because I guarantee you, people who study these things don't need to google it.

Very little I should think given the amount of ice still visible on calisto and ganymede especially in craters, which almost certainly don't have any kind of crustal convection. If it was any significant amount then these moons would be jet black after 4 billion years. So go ponder that one you smug bastard.

If Io were the only source of non-ice
material to Europa’s surface and no loss occurred, then
using the flux values from Table 1, sulfur compounds could
be present on the surface at ~7% (molar abundance) relative
to H2O, while Na and Cl could reach 0.3%. Silicon and
magnesium could be comparable or slightly less than Na
and Cl. These estimates assume uniform mixing and ignore
hemispherical flux and gardening rate differences, which
can produce surface concentrations that are a factor of 10
or more different between the leading and trailing sides (see
Fig. 2 and caption).

Seems to me that there could be quite a bit of material present. Much from Io outgassing and 'splash' from impactors to IO settling on Europa, not even counting direct impacts to Europa.

Unlike you however, I openly admitted to having little knowledge aside from a cursory glance at a paper on the subject. That is far from hypocritical.,br>
You on the other hand seem to want to be acknowledged as an expert with little more than a 'fuck you I'm smart". But I think most here can see through your ego.

Seriously? Which part of "I suspect" and "There may well be" in my original post do you have a problem comprehending, because its seems like simple fucking english to me. If english is your second language I'd suggest learning it a bit better, if not thenbuy yourself a nice spade for christmas, it'll help you did that hole even faster.

The earliest claimed fossilized lifeforms on earth are as old as old as 4.28 billion years old. it suggests an almost instantaneous emergence of life after oceans formed 4.4 billion years ago. Obviously Europa doesn't have the same conditions as early earth but perhaps the Abiogenesis is simply slower instead of impossible under those conditions and Europa has had plenty of time. We just don't know

Where from? The amounts of rock minerals from space dust and organics from reactions on the surface are probably minute.

Io is right next door (so to speak), and spews forth a lot of material from its volcanoes. Some of that material makes it into the Jovian space between the moons. Jupiter's magnetic field is a transport mechanism.

Also: we know that tons - literally, tons [iflscience.com] - of extraplanetary material rains down on the Earth each day. Jupiter, being as massive as it is, probably sucks up a lot more. Europa is a small target, but is traveling through this inward flux of material and is sure to pick some up.

Except the surface of Europa is red-brown specifically because something is accumulating. The two competing ideas are either it is organic compounds due to UV interacting with carbon and nitrogen coming from below the ice, or a combination of sulfur and magnesium coming from off the moon. Results of Galileo lean toward the latter. Depending on the geology of the rock below the ice and ocean, sulfur from rock may be very small compared to what hits the surface.

Anyway, we have no idea what conditions are required for life to start. There may well be a minimum energy requirement which europa doesn't even get close to. Also you need some kind of energy gradiant. In an ocean sealed off dozens or even hundreds of km below the surface I suspect that gradient is shallow in the extreme.

Features such as Conamara chaos [wikipedia.org] show extensive melt-through and rafting. That does not happen with an icy crust hundreds of kilometres thick.

The ice shell is probably less than 10km thick in most places and occasionally much thinner. Gives ample opportunity for surface materials (irradiated by the sun and radiation from jupiter) to be recycled into the subsurface ocean.

Jupiter is *the* gravitational trash compactor for the whole solar system. Earth collects around 50 tons of space dust a day, and that doesn't include the significant larger chunks of stuff that fall intermittently. We're in the kiddy pool version of gravitationally stretched space, at least compared to the Mariana Trench that that is Jupiter. I would imagine a commensurately greater amount of crap is swirling in the region of Jupiter and as a

- A mix of black and white on the surface, but due to its history, they're mostly separated.- The distribution of its "assets" (mass) is far from equilibrium.- A violent history- A bulging waistline (with a belt)- Elected a mentally-challenged racist as its president (I assume based on no evidence)

I always anticipated this. Tidal forces affect liquids far more than rock or hot pressurized rock (mantle). I mean IO doesn't have anywhere near the amount of water that Europa does and it's being torn and scewed by these immense forces.

I don't see how this makes it more habitable however as large glacial tectonic forces, while similar is appearance to regulr tectonics don't seem to make life any easier on the surface. If anything it makes it more difficult to establish any kind of surface base given how quickly the ice can shift compared to normal mantle based tectonics.

As par for the course I didn't RTFA. So I don't know if the title and summary have nothing to do with each other and follow the inflammatory trend of clickbait or not.

However I'm not sure what "New Evidence" they are referring to other than someone built a simulated model. A model demonstrating something isn't exactly evidence. Depending on the parameters, you can build a model to show just about anything you want to show. If you are trying to show ice tectonics by using a model, I'm pretty sure you can do